1. Field of the Invention
The present invention relates to a brake apparatus and, more particularly, to an electric brake apparatus having a brake motor which is rotated in a normal direction so as to generate a braking force and rotated in a reverse direction so as to cancel the braking force.
2. Description of the Related Art
Japanese Laid-Open Patent Application No.7-291120 discloses an electric brake apparatus having a disc brake which includes an electrically driven caliper and a disc rotor rotating with a wheel. The electrically driven caliper is driven by a brake motor so as to generate a clamping force. When a power supply to the brake motor is stopped, the clamping force of the electrically driven caliper is cancelled. More specifically, the brake motor moves brake pads provided on the electrically driven caliper toward the disc rotor so that a braking force is generated by the brake pads being pressed against the disc rotor. In order to cancel the braking force, the brake motor moves the brake pads in a direction opposite to the direction toward the disc rotor. Hereinafter, the rotation of the brake motor in the direction to generate the braking force is referred to as a normal rotation, and the direction of the normal rotation is referred to as a normal direction. Additionally, the rotation of the brake motor in a direction to cancel the braking force is referred to as a reverse rotation, and the direction of the reverse rotation is referred to as a reverse direction.
When the brake motor is rotated in the reverse direction, there may be a case in which the brake motor is driven by an excessive power. In such a case, parts provided around a motor shaft of the brake motor may be damaged due to excessive rotation. Additionally, a clearance gap between the disc rotor and the brake pads is increased, which increases a response time of a subsequent braking operation. Accordingly, in order to prevent the parts from being damaged and maintain a quick response of a braking operation, it is necessary to appropriately prevent the brake motor from being excessively rotated in the reverse direction.
In the conventional brake apparatus, a mechanical clutch is provided so as to disengage the brake motor from the caliper when an excessive power is generated by the brake motor in the reverse direction so that the excessive power is not transmitted to the caliper. However, there is a problem in that the entire structure of the electric brake apparatus is complex due to addition of the mechanical clutch.